Changes of the level of G protein alpha-subunit mRNA by tolerance to and withdrawal from butorphanol

Alterations in the levels of heterotrimeric G protein subunits induced by psychostimulants, opiates, barbiturates, and ethanol: Implications for drug dependence, tolerance, and withdrawal

Neuronal adaptations have been found to occur in multiple brain regions after chronic intake of abused drugs, and are therefore thought to underlie drug dependence, tolerance, and withdrawal. Pathophysiological changes in drug responsiveness as well as behavioral sequelae of chronic drug exposure are thought to depend largely upon the altered state of heterotrimeric GTP binding protein (G protein)-coupled receptor (GPCR)-G protein interactions. Responsiveness of GPCR-related intracellular signaling systems to drugs of abuse is heterogeneous, depending on the types of intracellular effectors to which the specific Galpha protein subtypes are coupled and GPCR-G protein coupling efficiency, factors influenced by the class of drug, expression levels of G protein subunits, and drug treatment regimens. To enhance understanding of the molecular mechanisms that underlie the development of pathophysiological states resulting from chronic intake of abused drugs, this review focuses on alterations in the expression levels of G protein subunits induced by various drugs of abuse. Changes in these mechanisms appear to be specific to particular drugs of abuse, and specific conditions of drug treatment.

Opioid abuse and brain gene expression

Opiate addiction is a central nervous system disorder of unknown mechanism. Neuronal basis of positive reinforcement, which is essential to the action of opioids, relies on activation of dopaminergic neurons resulting in an increased dopamine release in the mesolimbic brain structures. Certain aspects of opioid dependence and withdrawal syndrome are also related to the activity of noradrenergic and serotonergic systems, as well as to both excitatory and inhibitory amino acid and peptidergic systems. The latter pathways have been recently proven to be involved both in the development of dependence and in counteracting the states related to relapse. An important role in neurochemical mechanisms of opioid reward, dependence and vulnerability to addiction has been ascribed to endogenous opioid peptides, particularly those acting via the mu- and kappa-opioid receptors. Opiate abuse leads to adaptive reactions in the nervous system which occur at the cellular and molecular levels. Recent research indicates that intracellular mechanisms of signal transmission-from the receptor, through G proteins, cyclic AMP, MAP kinases to transcription factors--also play an important role in opioid tolerance and dependence. The latter link in this chain of reactions may modify synthesis of target genes and in this manner, it may be responsible for opiate-induced long-lasting neural plasticity.

Colforsin analogues: tritiation and characterization

Methods are presented to tritiate and characterize colforsin analogues 2 and 3.